Although key-operated locking mechanical systems may provide adequate protection in most situations, there are some drawbacks associated with their use. Firstly, keys for the most part can be easily copied and distributed to unauthorized users. Also, if the key is ever lost or stolen, it might be necessary to replace the whole lock cylinder in order to assure that an unauthorized user does not gain access. This can be a significant disadvantage in some cases. For example, it could be costly and rather inconvenient for a business location having many employees to replace a lock cylinder each time an employee loses his key.
As an alternative to conventional key-operated mechanical locking systems, locking arrangements were designed which utilize electronic access control means for keyless entry. U.S. Pat. No. 5,447,047 discloses a keyless entry deadbolt locking system wherein an electronic access control means, in the form of a decoding means, is located next to the knob on the outside of the door. When the decoding means is decoded by an authorized user, a coil is energized such that a rod is moved rightward and the extensions of the rod are caused to engage with grooves of a disc whereby a shaft can be rotated and the door can be opened. Although the deadbolt offers security against prying, one of the disadvantages of this locking system is that the electronic access control means can be accessed from the outside, and thus can be tampered with.
German Patent 198 51 308, the contents of which are incorporated herein by reference, describes a locking system for a door wherein the access control means is located within a knob on the inside of the door. The electronic access control means comprises a wireless data signal receiver which receives signals transmitted from a remote transmitter operated by a user. Once an authorized signal is recognized by the access control means, a solenoid is activated to control a coupling element which in turn allows the lock to be moved in a locked or unlocked position using a knob on the outside of the door. Since the remote transmitter transmits data signals using an alternating magnetic field, data signals can be transmitted with acceptable reception quality through even highly secure metal laminated doors. This allows the access control means to be placed on the inside of the door where it would be protected against tampering from the outside. However, this is only advantageous with locking cylinder standards which consist of a single element that goes through the whole door. The U.S. standard cylinder is a single cylinder. So the electronics in the knob are on the outside and can easily be manipulated. If the access control means are located on the inside of the door, an expensive through connection is necessary, which is dependent on the type of door and lock and which is furthermore difficult to install.
U.S. Pat. No. 5,531,086 discloses a keyless entry deadbolt lock arrangement for a door wherein the access control means is located within the door. The deadbolt lock arrangement can be opened manually by inserting a key or operating a switch, or opened remotely by using a RF (radio frequency) remote controller to activate an actuator that places the lock in a locked or unlocked position. Since reception of the wireless signal by the access control means located within the door can pose a problem depending on the type of door, the top portion of the housing containing the locking cylinder is provided with openings in order to permit better reception of the signal transmitted by the remote transmitter.
U.S. Pat. Appl. No. 2004/0255628, the contents of which are incorporated herein by reference, describes an electronic lock system with improved lock and transponder for securing a door that is easy to install and can easily be retrofitted. The keyless electronic door lock system has an access control means which is located within the cylinder body of the lock.
Some electronic locks require a coupling interface that transmits the movement from the outside handle to the latch to open the door in the unlocked state (coupled state) and to allow for the handle to rotate, but not transmit, the movement to the latch in the locked state (decoupled state). DE-C-37 42 189 discloses a lock cylinder, the coupling of which is connected to the locking bit and can be brought into engagement on one side with a bossed shaft. In order to configure such a lock cylinder in a more simple manner and to achieve better protection against unauthorized use of the lock cylinder, it is proposed that the bossed shaft be enclosed by a locking sleeve which can be displaced axially by the coupling and secured in certain positions.
EP-A-1 072 741 discloses a lock cylinder, in particular, an electronic lock cylinder with electromechanical rotational blocking in which the electronic key has opposing electrical terminals on the shaft and the rotatable core of the lock cylinder has an external annular track that is electrically conducting, and with its inner face, communicates with an electrical contact supported on the terminal whereas the external annular track is supported in the electrical brushes of the external and internal rotors.
EP-A-0 743 411 discloses a lock device in which the key of the lock device comprises a code transmitter formed by a transponder. An actuator, a transponder reading device, and a power supply device are arranged in the cylinder housing of the lock cylinder of the lock means. The actuator serves for displacing a locking means which locks or releases the cylinder core and which engages at the circumference of the cylinder core.
EP-A-1 079 050 discloses a lock means comprising a lock bit being blockable by a locking mechanism, wherein a coupling is arranged between the blocking mechanism and the lock bit. The coupling can be separated from only one side of the lock means. The lock means should thus be unlockable from this side without any access authorization for the locking mechanism.
EP-B-0 805 905 discloses a closing mechanism for a door comprising a spindle, an actuating means turning the spindle, a locking element in functional connection with the spindle to lock the door, and a coupling element fitted in the actuating means and acting on the rotation of the spindle. The coupling element moreover has a pin which moves to and from axially to the spindle and which can be moved to and fro via a spindle by means of a locking element arranged independent of the actuating means via an electric motor drivable by means of an electronic control in order for either to transmit the rotation of the freely rotatable actuating means to the spindle or, in the case of an actuating means, being rigidly connected with the shaft to allow only a slight rotation of the actuating means connected with the shaft. Moreover, a cam is formed on the pin and a spiral spring is clamped as a force storage means between the cam and the spindle of the electric motor, and on the front surface of the actuating means a contact disk is provided via which the electronic control from an electronic information carrier can be controlled via data exchange.
Known coupling interface devices and methods of this kind prove to be disadvantageous in that relatively much energy is demanded for shifting the coupling or lock element that forces acting on the coupling element in the coupled and decoupled states and causes a load of the lock element and that a load of the coupling element or lock element is transmitted to the drive or actuator.
U.S. patent application Ser. No. 10/705,021 published as 2005/0050929, the contents of which are incorporated herein by reference, describes an electronic lock that requires relatively little energy for shifting the coupling or lock element. The coupling mechanism is shifted into the coupled and decoupled states by a bi-stable actuator that is powered by batteries. The actuator rotates to move a coupling locking element into a position where it causes the lock to be in a coupled state. The coupling locking element moves in a linear direction. In the coupled state, the coupling locking element allows for the rotational force from the exterior knob to be transferred to the latch in order to open the door. In the decoupled state, the rotational force from the exterior knob is not transferred to the latch.
U.S. Pat. Appl. No. 10/556,012 published as 2007/0137326, the contents of which are incorporated herein by reference, describes an electronic lock with a coupling locking element that is positioned between two reel elements in the coupled state so that reels can overcome the mechanical potential of a take-off, and thereby cause the latch to operate. In the decoupled state, the coupling locking element is not positioned between the reels, and the reels cannot overcome the mechanical potential of the take-off.
The coupling interface and/or actuator may not be configured to handle the stress of the forces exerted by the user, especially when excessive force is exerted through a lever. The transmission of forces to the drive or actuator can result in increased wear and reduced functional safety. In the United States, building codes may require that locks have levers, and levers can transmit large amounts of torque to a lock. Low-energy electronic lock mechanisms may not be strong enough to handle the torque from a lever without breaking or wearing down.
Electronic access control devices may be susceptible to tampering, especially when the lock circuitry and/or actuator are/is located within the exterior handle. Electronic locks utilizing magnetic/electromagnetic actuators should be secured against tampering by an applied external magnetic field.
It can also be difficult to install or retrofit electronic control devices in doors, file cabinets, drawers, cabinets, and other closure panels because the electronic control devices can require hardwiring to receive power and to communicate control signals to a central access control computer.